<HTML>
<BODY BGCOLOR="white">
<PRE>
<FONT color="green">001</FONT>    package net.jmatrix.util;<a name="line.1"></a>
<FONT color="green">002</FONT>    <a name="line.2"></a>
<FONT color="green">003</FONT>    <a name="line.3"></a>
<FONT color="green">004</FONT>    import java.util.*;<a name="line.4"></a>
<FONT color="green">005</FONT>    import java.lang.reflect.*;<a name="line.5"></a>
<FONT color="green">006</FONT>    <a name="line.6"></a>
<FONT color="green">007</FONT>    import net.jmatrix.eproperties.EProperties;<a name="line.7"></a>
<FONT color="green">008</FONT>    <a name="line.8"></a>
<FONT color="green">009</FONT>    import java.util.logging.*;<a name="line.9"></a>
<FONT color="green">010</FONT>    import static java.util.logging.Level.*;<a name="line.10"></a>
<FONT color="green">011</FONT>    <a name="line.11"></a>
<FONT color="green">012</FONT>    <a name="line.12"></a>
<FONT color="green">013</FONT>    /**<a name="line.13"></a>
<FONT color="green">014</FONT>     * The InstanceFactory builds instances of classes based on <a name="line.14"></a>
<FONT color="green">015</FONT>     * properties files.  These can then be cast to appropriate types<a name="line.15"></a>
<FONT color="green">016</FONT>     * as necessary.<a name="line.16"></a>
<FONT color="green">017</FONT>     */<a name="line.17"></a>
<FONT color="green">018</FONT>    public final class InstanceFactory <a name="line.18"></a>
<FONT color="green">019</FONT>    {<a name="line.19"></a>
<FONT color="green">020</FONT>       static final Logger log=Logger.getLogger(InstanceFactory.class.getName());<a name="line.20"></a>
<FONT color="green">021</FONT>       <a name="line.21"></a>
<FONT color="green">022</FONT>       /** */<a name="line.22"></a>
<FONT color="green">023</FONT>       static Map&lt;String, Constructor&gt; constructorCache=new HashMap();<a name="line.23"></a>
<FONT color="green">024</FONT>    <a name="line.24"></a>
<FONT color="green">025</FONT>       /** <a name="line.25"></a>
<FONT color="green">026</FONT>        * Builds a new instance of a class based on an EProperties file.<a name="line.26"></a>
<FONT color="green">027</FONT>        * The properties MUST CONTAIN: <a name="line.27"></a>
<FONT color="green">028</FONT>        *  - 'class' which is the fully qualified (with package) class name <a name="line.28"></a>
<FONT color="green">029</FONT>        *    of the implementing class.<a name="line.29"></a>
<FONT color="green">030</FONT>        * <a name="line.30"></a>
<FONT color="green">031</FONT>        * The class defined above MUST be available in the current JVM<a name="line.31"></a>
<FONT color="green">032</FONT>        * CLASSPATH.  Ie, Class.forName(class) must resolve.<a name="line.32"></a>
<FONT color="green">033</FONT>        * <a name="line.33"></a>
<FONT color="green">034</FONT>        * The Class defined above MUST have at least 1 constructor that <a name="line.34"></a>
<FONT color="green">035</FONT>        * take an EProperties object as a parameter.  These properties<a name="line.35"></a>
<FONT color="green">036</FONT>        * are passed to the implementing class's constructor.<a name="line.36"></a>
<FONT color="green">037</FONT>        *<a name="line.37"></a>
<FONT color="green">038</FONT>        * Users of this class will always cast the resulting object <a name="line.38"></a>
<FONT color="green">039</FONT>        * to the appropriate type.<a name="line.39"></a>
<FONT color="green">040</FONT>        *<a name="line.40"></a>
<FONT color="green">041</FONT>        * @param EProperties The properties object which defines the class<a name="line.41"></a>
<FONT color="green">042</FONT>        * and any parameters for its construction.<a name="line.42"></a>
<FONT color="green">043</FONT>        * @return An Object, which is an instance of the class requested.<a name="line.43"></a>
<FONT color="green">044</FONT>        */<a name="line.44"></a>
<FONT color="green">045</FONT>       public static Object buildInstance(EProperties props) <a name="line.45"></a>
<FONT color="green">046</FONT>          throws InstantiationException, ClassNotFoundException, <a name="line.46"></a>
<FONT color="green">047</FONT>          NoSuchMethodException, IllegalAccessException, <a name="line.47"></a>
<FONT color="green">048</FONT>          InvocationTargetException {<a name="line.48"></a>
<FONT color="green">049</FONT>          // This method makes 3 assumptions:<a name="line.49"></a>
<FONT color="green">050</FONT>          // 1) The properies file contains a string property <a name="line.50"></a>
<FONT color="green">051</FONT>          //    called 'class' - which is the class name of the <a name="line.51"></a>
<FONT color="green">052</FONT>          //    implmementation class<a name="line.52"></a>
<FONT color="green">053</FONT>          // 2) The class specified in 'class' exists in the current <a name="line.53"></a>
<FONT color="green">054</FONT>          //    classpath.<a name="line.54"></a>
<FONT color="green">055</FONT>          // 3) The class has a public constructor that takes an <a name="line.55"></a>
<FONT color="green">056</FONT>          //    EProperties object.<a name="line.56"></a>
<FONT color="green">057</FONT>    <a name="line.57"></a>
<FONT color="green">058</FONT>          Object target=null;<a name="line.58"></a>
<FONT color="green">059</FONT>          String className=props.getString("class");<a name="line.59"></a>
<FONT color="green">060</FONT>    <a name="line.60"></a>
<FONT color="green">061</FONT>          log.log(FINE, "InstanceFactory: building instance of "+className);<a name="line.61"></a>
<FONT color="green">062</FONT>          if (className == null) {<a name="line.62"></a>
<FONT color="green">063</FONT>             throw new RuntimeException("InstanceFactory: ERROR.  Property "+<a name="line.63"></a>
<FONT color="green">064</FONT>                                        "'class' is required.  Inbound "+<a name="line.64"></a>
<FONT color="green">065</FONT>                                        "properties does not contain 'class'");<a name="line.65"></a>
<FONT color="green">066</FONT>          }<a name="line.66"></a>
<FONT color="green">067</FONT>    <a name="line.67"></a>
<FONT color="green">068</FONT>          if (className == null) {<a name="line.68"></a>
<FONT color="green">069</FONT>             throw new <a name="line.69"></a>
<FONT color="green">070</FONT>             IllegalArgumentException("InstanceFactoryr: Required property "+<a name="line.70"></a>
<FONT color="green">071</FONT>                                      "class which defines the "+<a name="line.71"></a>
<FONT color="green">072</FONT>                                      "implementation class is null.  Props must "+<a name="line.72"></a>
<FONT color="green">073</FONT>                                      "contain 'class' property.");<a name="line.73"></a>
<FONT color="green">074</FONT>          }<a name="line.74"></a>
<FONT color="green">075</FONT>          Constructor constructor=getConstructor(className);<a name="line.75"></a>
<FONT color="green">076</FONT>    <a name="line.76"></a>
<FONT color="green">077</FONT>          target=constructor.newInstance(props);<a name="line.77"></a>
<FONT color="green">078</FONT>    <a name="line.78"></a>
<FONT color="green">079</FONT>          return target;<a name="line.79"></a>
<FONT color="green">080</FONT>       }<a name="line.80"></a>
<FONT color="green">081</FONT>       <a name="line.81"></a>
<FONT color="green">082</FONT>       /** */<a name="line.82"></a>
<FONT color="green">083</FONT>       public static Object runtimeBuildInstance(EProperties p) {<a name="line.83"></a>
<FONT color="green">084</FONT>          try {<a name="line.84"></a>
<FONT color="green">085</FONT>             return buildInstance(p);<a name="line.85"></a>
<FONT color="green">086</FONT>          } catch (Exception ex) {<a name="line.86"></a>
<FONT color="green">087</FONT>             throw new RuntimeException("Error building instance!", ex);<a name="line.87"></a>
<FONT color="green">088</FONT>          }<a name="line.88"></a>
<FONT color="green">089</FONT>       }<a name="line.89"></a>
<FONT color="green">090</FONT>    <a name="line.90"></a>
<FONT color="green">091</FONT>       /** */<a name="line.91"></a>
<FONT color="green">092</FONT>       private static final Constructor getConstructor(String className) <a name="line.92"></a>
<FONT color="green">093</FONT>          throws InstantiationException, ClassNotFoundException, <a name="line.93"></a>
<FONT color="green">094</FONT>          NoSuchMethodException {<a name="line.94"></a>
<FONT color="green">095</FONT>          Constructor constructor=constructorCache.get(className);<a name="line.95"></a>
<FONT color="green">096</FONT>          <a name="line.96"></a>
<FONT color="green">097</FONT>          if (constructor == null) {<a name="line.97"></a>
<FONT color="green">098</FONT>             log.log(FINE, "InstanceFactory: caching constructor for '"+className+"'");<a name="line.98"></a>
<FONT color="green">099</FONT>             constructor=buildConstructor(className);<a name="line.99"></a>
<FONT color="green">100</FONT>          }<a name="line.100"></a>
<FONT color="green">101</FONT>          return constructor;<a name="line.101"></a>
<FONT color="green">102</FONT>       }<a name="line.102"></a>
<FONT color="green">103</FONT>    <a name="line.103"></a>
<FONT color="green">104</FONT>       /** */<a name="line.104"></a>
<FONT color="green">105</FONT>       private static final Constructor buildConstructor(String className) <a name="line.105"></a>
<FONT color="green">106</FONT>          throws InstantiationException, ClassNotFoundException, <a name="line.106"></a>
<FONT color="green">107</FONT>          NoSuchMethodException {<a name="line.107"></a>
<FONT color="green">108</FONT>          Class clazz=Class.forName(className);<a name="line.108"></a>
<FONT color="green">109</FONT>             <a name="line.109"></a>
<FONT color="green">110</FONT>          // I apologize in advance for this obscure syntax.  Bemo.<a name="line.110"></a>
<FONT color="green">111</FONT>          Constructor constructor=clazz.getConstructor(new Class[]{EProperties.class});<a name="line.111"></a>
<FONT color="green">112</FONT>          constructorCache.put(className, constructor);<a name="line.112"></a>
<FONT color="green">113</FONT>          return constructor;<a name="line.113"></a>
<FONT color="green">114</FONT>       }<a name="line.114"></a>
<FONT color="green">115</FONT>    }<a name="line.115"></a>




























































</PRE>
</BODY>
</HTML>
